Trencadís is a type of mosaic

Mosaic

Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials. It may be a technique of decorative art, an aspect of interior decoration, or of cultural and spiritual significance as in a cathedral...

 created from broken tile shards. The technique is also called pique assiette

Pique assiette

Pique Assiette is a form of art similar to mosaic but specifically uses broken plates and the like arranged in patterns or designs. The name comes from the French pique-assiette, meaning "one who eats from others' plates". It is or as in the French...

.
This mosaic is done thanks to broken pieces of ceramic like tiles and cups, for instance.

Antoni Gaudí was the first to use this technique. He covered his three-dimensional architecture with ceramics of different shapes, reliefs and colours, collected from the factory "Pujol i Bausis" located in Esplugues de Llobregat, which create brightly-colored patterns dancing together under the Mediterranean light.

The Catalan architects Antoni Gaudí

Antoni Gaudí

Antoni Gaudí i Cornet was a Spanish Catalan architect and figurehead of Catalan Modernism. Gaudí's works reflect his highly individual and distinctive style and are largely concentrated in the Catalan capital of Barcelona, notably his magnum opus, the Sagrada Família.Much of Gaudí's work was...

 and Josep Maria Jujol

Josep Maria Jujol

Josep Maria Jujol Gibert was a Catalan architect.Jujol's wide field of activity ranged from furniture designs and painting, to architecture. He worked with Antoni Gaudí on many of his most famous works.-Biography:...

 used trencadís in many projects, among which Barcelona

Barcelona

Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...

's Parc Güell is probably the most famous.